Axial pouring-nozzle structure for rotary melting furnace

ABSTRACT

The nozzle structure has a substantially frustoconical profile of revolution about the axis of rotation of the furnace and comprises a metallic partition system which provides recesses having their openings on the internal periphery of said profile, ceramic bricks which are fitted within the recesses and fluidcircuits for cooling the partition system.

iJiiite States atent Yerouchaimi [s4] AXIAL POURING-NOZZLE STRUCTURE FOR ROTARY MELTING FURNACE [72] inventor: David Yerouchalmi,3 rue de Lldle de France 78, be Mesnil, Saint Denis, France 221 Filed: on. 16,1970

211 Appl.No.: 81,343

[30] Foreign Application Priority Data Oct. 24, 1969 France ..6936565 [52] US. Cl ..263/33 R, 263/44, 263/46 [51] Int. Cl ..F27b 7/20 [58] Field of Search ..263/33, 44, 46

[56] References Cited UNITED STATES PATENTS 3,510,115 5/1970 Foex et al. ..263/33 R 2,175,291 10/1939 Heskett ..263/46 2,137,184 11/1938 Seil ..263/46 Primary Examiner-John J. Camby Attorney-Lane Aitken Dunner & Ziems ABSTRACT The nozzle structure has a substantially frustoconical profile of revolution about the axis of rotation of the furnace and comprises a metallic partition system which provides recesses having their openings on the internal periphery of said profile, ceramic bricks which are fitted within the recesses and fluid-circuits for cooling the partition system.

9 Claims, 2 Drawing Figures PATENTEDUEC 12 I972 3 705, 7 1 2 sum 1 or 2 INVENTOR DAVID YE ROUCHALMI ORNEYS PATENTED DEC 12 I972 SHEET 2 OF 2 INVENTOR DAVID YEROUCHALMI I W W W A ()RNEYS AXIAL POURING-NQZZLE STRUCTURE FOR ROTARY MELTING FURNACE This invention relates to an axial pouring nozzle structure for a rotary melting furnace and more precisely to a nozzle structure having a regulated surface temperature for a rotary furnace which is intended to melt highly refractory materials. In a rotary melting furnace, the material to be melted which can be a simple or composite refractory oxide or which can equally well be either a refractory metal or an element such as carbide, boride, silicide, nitride, sulphide and so forth is charged into a rotary cylindrical shell having a horizontal axis and provided with cooling systems, there being formed in said shell a central cylindrical cavity constituting the heating zone in which a suitable thermal flux penetrates through the axial openings provided at both ends of said cavity. Melting takes place in the central portion of said charge of refractory material (approximately one-third of the total volume charged) whereas the remainder forms a gradual-sintering zone in which the sintering rate decreases towards the cooled shell walls. This is known as melting in an automatic crucible.

In order to ensure economic performance of this melting process, it is necessary to recover the molten mass immediately. In point of fact, if this mass is allowed to cool within the furnace, this latter is kept out of operation throughout the cooling period which can last up to several hours and it is then necessary to dismantle the end walls of the furnace in order to extract the cooled monolithic part. Said part which is surrounded with powder must then be trimmed and crushed in the form of granules which are ready to be re-shaped and sintered to the dimensions required by the user. These different operations obviously take a fairly long time and the economic performance of the furnace is of a very low order. For example, it follows from the foregoing that, in order to obtain 20 liters of zirconia in a rotary furnace which is heated by means of plasma torches and in which a melting time of 8 to 10 minutes is required in order to melt said 20 liters, it is therefore necessary to wait approximately 3 hours before dismantling of the furnace can be undertaken. Since this operation and the treatment of the monolithic part entail a further period of three hours, the total time which elapses between two successive heats is 6 hours. It is therefore apparent that the economic performance of the furnace is very considerably enhanced if there is a possibility of recovering the molten mass immediately by tilting the furnace.

Although pouring of the molten mass does not present any particular problem when working at temperatures which do not exceed 2,000 C., this operation does nevertheless gives rise to problems relating to behavior of materials and geometry of the discharge opening at the very high temperatures which are attained when making use of focused solar energy (approximately 2,800 C. superoxidized flames (approximately 3,000 C.) or plasma sources (4,55 to 5,000C.). In this case, the opening which performs the function of pouring noule must essentially be located at one end of the furnace. In fact, it would not be feasible to provide the opening in the central portion of the furnace and to close it off with a plug of refractory material as is the practice in some rotary furnaces which operate at relatively low temperatures since this solution would present almost insuperable problems of technological development by reason of the need to pass through the cooling zone of the shell. Moreover, the danger of solidification of the molten mass in the discharge passage would be very considerable. It is therefore clear that the outlet for the molten mass must be one of the two axial openings at the ends of the furnace. Moreover, it must be possible to carry out the discharge through a nozzle which rotates at a low speed (50 to revolutions per minute) in order to prevent formation of hot points which would result in dissymmetrical wear of the nozzle and in formation of trails of solidified lava. Finally, the surfaces of the pouring nozzle which are in contact with the molten material must undergo controlled cooling in order to prevent the possibility of damage especially as a result of melting but without causing solidification of the lava which would be liable to obstruct the outlet.

The present invention proposes an axial pouring nozzle structure for a rotary furnace in which the abovementioned requirements are satisfied. This structure is mainly characterized in that it has a substantially frustoconical profile of revolution about the axis of rotation of said furnace and comprises a metallic partition system defining recesses which are open on the internal periphery of said profile, ceramic bricks fitted within said recesses and fluid-circuits for cooling said partition system.

Further characteristic features of the present invention will become apparent from the following description in connection with one preferred embodiment of said pouring nozzle structure for a rotary furnace of the type described in French PAT. No. 1,526,999 of Feb. 20, 1962 in the name of the present applicant.

Reference will be made in the description to the accompanying drawings which are given by way of explanation but not in any sense by way of limitation, and in which:

FIG. 1 is a diagrammatic presentation of said furnace;

FIG. 2 is a detailed presentation of the structure of the pouring nozzle in accordance with the invention, said furnace being equipped with said nozzle.

The rotary melting furnace which is illustrated in FIG. 1 comprises the following main components:

a rotary cylindrical shell I which may or may not be formed of heat-resistant metal and has a horizontal axis 00', the two ends of said shell being frustoconical and pierced by an axial duct 2,

two identical circular walls 3 having a central opening and attached to each frustoconical extremity of the shell, thus defining with said extremities two outer chambers 4', said walls are provided with a inwardly directed peripheral flange 5,

a stationary casing 6 surrounding the shell 1 externally of the flanges 5 of the end walls 3; rotational motion of the metal shell 1 is carried out within the interior of said casing by means of two ball-bearing raceways 7; transmission of motion is carried out by means of a driving shaft 8 which terminates in a pinion 9 and said pinion cooperates with a ringgear 10 which is concentric with the shell 1,

stationary fluid-circuits for cooling the rotary shell 1 and comprising spray tubes 11 which are distributed around the periphery of said shell and supplied with cooling liquid which is admitted from the exterior through pipes 12, two annular zones 13 which interconnect the extremities of said spray tubes, and tubes 14 which are supplied by said annular zones and deliver the cooling liquid into the end chambers 4; thus, part of the liquid which is delivered into said chambers flows upwards under the action of centrifugal force towards the top portion of the furnace and falls back onto the rotary shell 1; the cooling liquid is discharged through an opening 15 which is provided in the bottom portion of the stationary casing 6.

Pouring of the molten material 16 by tilting of the furnace can be carried out through either of the two axial openings 2 of the shell which form two nozzles having a frustoconical profile of revolution and therefore permit rotational motion of the furnace during the casting operation, the ceramic-metal structure of said nozzles as contemplated by the invention being shown .in detail in FlG. 2.

The wall of the shell 1 is provided in the end portion which defines the axial opening 2 with an annular reinforcement 17 of heat-resistant metal in which are formed recesses having their openings on the internal periphery of said reinforcement, the cross section of said recesses being progressively narrower from the base to the apex. Said metallic recesses are fitted with ceramic bricks 18 which have the same cross-section and the composition of which is similar to that of the material to be melted, said bricks being thus inset in the wall.

The same reinforcement 17 extends into the shell 1 over a predetermined length of the frustoconical extremity and forms in two concentric rings two further series of metallic recesses which open into the interior of the furnace. These recesses have substantially the same cross-section as those of the portion which is adjacent to the opening 2 and are also fitted with ceramic bricks 18.

Finally, the wall which serves to define the end chamber 4 in conjunction with the frustoconical portion of the shell 1 is provided around the axial opening 2 with a reinforcement 19 of heat-resistant metal so as to form an outer flange for the pouring nozzle. That portion of said reinforcement which defines the discharge opening 2 comprises a ring of metallic recesses which are open on its internal periphery and are also fitted with ceramic bricks l8. Said reinforcement comprises a second ring which is located externally of the first and consists of metallic recesses which have progressively narrower cross-sections towards the apex, said recesses being open to the exterior of the furnace and containing ceramic bricks 18.

Under these conditions and by reason of the presence of pipes 14 which deliver water into the end chamber 4, the ceramic bricks 18 are cooled laterally and at the bases thereof so that the mean value of temperature on the surface which is in contact with the molten material can be maintained in the vicinity of l,600 to 'l,700 C., a maximum value of 1,900 C. being permissible in certain cases in which the melting process has to take place at a temperature which is higher than 3,000 C. Said cooling action makes it possible to prevent melting of the walls of the pouring nozzle while preventing the molten material from solidifying on said walls.

The metallic framework of the bricks which serves to anchor these latter to the cooled metallic walls and also to subject said bricks to controlled cooling has a third function which is to retain the ceramic grains of the bricks 18 and to guard against the effects of erosion and abrasion which arise from the flow of molten lava.

It will be readily understood that this invention is not limited solely to the embodiment which has been described and illustrated by way of example and that the scope of this patent also extends to all alternative forms of either all or part of the arrangements described which remain within the definition of equivalent means as well as to any applications of such arrangements. In particular, there has been described a pouring nozzle structure as arranged in a furnace in which the rotary shell has frustoconical extremities and in which the nozzle profile conforms closely to that of said extremities. However, it is apparent that the structure in accordance with the invention applies to any type of melting furnace which makes use of a rotary cylindrical shell which is provided with axial openings at its extremities and that said structure can have any desired frustoconical profile. Moreover, provision can undoubtedly be made for any number of rings of ceramic bricks disposed around the periphery of the pouring nozzle.

What we claim is:

1. An axial pouring nozzle structure for a rotary melting furnace, wherein said nozzle structure has a substantially frustoconical profile of revolution about the axis of rotation of said furnace and comprises a metallic partition system defining recesses which are open on the internal periphery of said profile, said recesses having a cross-section which becomes progressively narrower from the base to the apex of said recesses, ceramic bricks fitted within said recesses and fluid-circuits for cooling said partition system.

2. A pouring nozzle structure according to claim 1, wherein said partition system is formed of heat-resistant metal.

3. A pouring nozzle structure according to claim 1, wherein said bricks have a composition which is similar to that of the material to be melted in the furnace.

4. A pouring nozzle structure according to claim 1, wherein the fluid-circuits for cooling the metallic partition system are stationary and comprise pipes for discharging a fluid onto the external periphery of the nozzle.

5. An axial pouring nozzle structure for a rotary melting furnace, wherein said nozzle structure has a substantially frustoconical profile of revolution about the axis of rotation of said furnace and comprises a first metallic partition system defining recesses which are open on the internal periphery of said profile, ceramic bricks fitted within said recesses, an annular flange around the terminal opening of the nozzle, a second metallic partition system mounted on said flange and defining recesses in which ceramic bricks are inserted, and fluid-circuits for cooling said partition systems.

6. Apouring nozzle structure according to claim 5, wherein said partition systems are formed of heat-resistant metal.

9. A pouring nozzle structure according to claim 5, wherein the fluid-circuits for cooling the metallic partition systems are stationary and comprise pipes for discharging a fluid onto the external periphery of the nozzle. 

1. An axial pouring nozzle structure for a rotary melting furnace, wherein said nozzle structure has a substantially frustoconical profile of revolution about the axis of rotation of said furnace and comprises a metallic partition system defining recesses which are open on the internal periphery of said profile, said recesses having a cross-section which becomes progressively narrower from the base to the apex of said recesses, ceramic bricks fitted within said recesses and fluid-circuits for cooling said partition system.
 2. A pouring nozzle structure according to claim l, wherein said partition system is formed of heat-resistant metal.
 3. A pouring nozzle structure according to claim 1, wherein said bricks have a composition which is similar to that of the material to be melted in the furnace.
 4. A pouring nozzle structure according to claim 1, wherein the fluid-circuits for cooling the metallic partition system are stationary and comprise pipes for discharging a fluid onto the external periphery of the nozzle.
 5. An axial pouring nozzle structure for a rotary melting furnace, wherein said nozzle structure has a substantially frustoconical profile of revolution about the axis of rotation of said furnace and comprises a first metallic partition system defining recesses which are open on the internal periphery of said profile, ceramic bricks fitted within said recesses, an annular flange around the terminal opening of the nozzle, a second metallic partition system mounted on said flange and defining recesses in which ceramic bricks are inserted, and fluid-circuits for cooling said partition systems.
 6. A pouring nozzle structure according to claim 5, wherein said partition systems are formed of heat-resistant metal.
 7. A pouring nozzle structure according to claim 5, wherein said bricks have a composition which is similar to that of the material to be melted in the furnace.
 8. A pouring nozzle structure according to claim 5, wherein said recesses have a cross-section which becomes progressively narrower from the base to the apex of said recesses.
 9. A pouring nozzle structure according to claim 5, wherein the fluid-circuits for cooling the metallic partition systems are stationary and comprise pipes for discharging a fluid onto the external periphery of the nozzle. 